This is beside the point of the original premise. If you wish to argue that, because some people are at a disadvantage, positive discrimination is not immoral, you may do so, but you have not done so here.
nobody

That may or may not be the case, but it does not address the premise that positive discrimination is immoral. You may argue that such effects offset the immorality of positive discrimination, but you have not done so.
nobody

This assumes that it is necessary and possible to "fix" such "existing wrongs and imbalances," and that it is necessary or possible to enforce a "level playing field," while leaving such a situation undefined.
nobody